1. Field of the Invention
This invention relates generally to methods and apparatus for burning liquid hyrdocarbon-containing matter, such as crude oil, emulsified oil based or inverted drilling fluids, and more particularly for burning the oil produced during a test of an offshore well with a minimum of environmental pollution.
2. Description of the Prior Art
When drill stem or production tests are performed on offshore wells, many problems arise in connection with the disposal of the hydrocarbons that are obtained in the test. For safety and practical reasons, it is highly undesirable to consider the storage of these products on or adjacent to the drilling platform. In addition, the loading and transport of such products by tanker involves many technical problems, can only be successfully accomplished in favorable weather, and may be comparatively costly. Accordingly, on-site burning of crude oil and gases has generally been considered to be the most desirable manner of disposal.
Such burning must, of course, be accomplished with minimum adverse environmental affects, hence with the creation of minimum smoke. In addition, crude oil burners must meet an additional number of requirements. First, they must be able to handle fluids containing solid particles and must be able to operate within a very wide range of flow rates, e.g. from a few cubic feet per hour to over twenty-four hundred cubic feet per hour. Of course, flow rate is necessarily dependent upon numerous operating variables, and can be expected to fluctuate considerably. Moreover, the burning process generates a considerable amount of heat and it is necessary to protect the personnel and equipment on the drilling platform. As mentioned, so-called smokeless burning is a prime requisite and this condition must be maintained despite changes in crude oil flow rate and drastic changes in wind direction and velocity.
A substantial number of prior art patents have proposed to minimize the smoke problem through the injection of water droplets or mist into the burning area of the crude oil, which, of course, sometimes is atomized through the application thereto of compressed air or combustible natural gases to promote the combustion of the crude oil particles.
Some prior art approaches, for example U.S. Pat. No. 3,807,932 to DeWald, have proposed the direct injection and atomization of the water in the same nozzle structure as employed for the combustible gases. This approach has the disadvantage of requiring substantially higher ignition temperatures, hence the production of considerable smoke during start up.
A number of prior art patents, for example British Pat. No. 1,400,549, have proposed that the water droplets be applied to the atomized oil by utilization of a ring of water nozzles each directing a cone-shaped pattern of atomized water upon a central burning cone of atomized fuel oil and combustible gases. This patent contains a discussion of the alleged desirability of injecting sprays of water droplets into the flame produced by the combustion of the crude oil in such a manner that the droplets penetrate into the flame but do not pass completely therethrough. The objective is, of course, to provide maximum exposure of the burning crude oil to the water droplets which, under the high temperature normally existing in such a combustion area results in the formation of hydrocarbons which substantially reduce the creation of smoke representing unburned crude oil components.
Such an arrangement is, nevertheless, not completely acceptable because a sudden change in wind direction or velocity may greatly affect the penetration of the water sprays into the combustible zone and result in the production of smoke until wind conditions again stabilize and the optimum quantity of water droplets is again injected into the combustion zone.